Skip to main content

Full text of "Guide for beginning fossil hunters"

See other formats


CniA Sxxuxyu^ 



£e^ie^ 4 



U0O>E ¥©U 



"V- " " 



■ r : 

3 jo 






BEGINNING 
FOSSIL HUNTERS 



Charles W. Collinson 




laiNOlS GEOLOGICAL 

SURVEY LIBRARY 

JUL 16 W* 



9lUwib State Q&dcKfical Suaaj^ 



STATE 




of ILLINOIS 

William G. Stratton, Governor 

DEPARTMENT of 
REGISTRATION and EDUCATION 
Vera M. Binks, Director 



ILLINOIS STATE GEOLOGICAL SURVEY 



3 3051 00004 7385 



ILLINOIS STATE 
GEOLOGICAL SURVEY 
John C. Frye, Chief 
URBANA, ILLINOIS 



IJUKH — 5-56) 



GUIDE FOR 

BEGINNING FOSSIL HUNTERS 

Gkcvde& W. G&lUukm 




9lL4AfricrfMm4- Wf Mgaa& Z. Irftewi 



Printed by Authority of the sun- of Illinois 



GUIDE FOR 

BEGINNING FOSSIL HUNTERS 

Charles W. Collinson 



v^BTOONG before your birth, long before your 
fi/v/^ grandfather and grandmother were born, 
g j%p : jeven before there were any men or the 
r<fci ^Mississippi River existed, there were ani- 
ViJ^r.7; v ^rnals on the earth. 

You may ask, "If there were no men around to 
see them, how do we know that there were animals 
then?" 

That question is pretty easy to answer, for the 
animals left their marks behind and we call those 
marks fossils. 

Some fossils are just foot tracks or worm holes. 
Others were made when mud sifted into empty 
shells and slowly turned to stone. Many bones or 
shells, even some skin and hair, have been pre- 
served in the rocks for millions of years. 




Of course the rocks in ^SSSGSZ 35^ 

which the fossils are en- ^^*$WI/$ 

cased weren't always rocks. 
At one time the sediments were just mud or sand 
on the floor of the sea; some were sand dunes on 
an ancient land. As time passed the sediments were 
buried under more sand or mud, and with the pass- 
ing of more time the sand and mud became rock. 



The fossils in the rocks, however, are only a 
small part of all the life that has existed on our 
planet. For every fossil we see, millions of ani- 
mals and plants have lived, died, and been destroyed 
without leaving a trace. However, by carefully col- 
lecting fossils and recording the layers of rocks 
they came from, we can reconstruct hundreds of 
generations that have lived on earth at one time or 
another since the beginning. 

Finding and collecting fossils not only helps to 
write missing chapters of earth history but is also 
an exciting adventure. It is an animal hunt - a hunt 
for creatures often more strange than any living on 
earth today. 

Your first fossil discovery will be a thrill. Later 
you will find that a search through a quarry or a 
strip mine is an excursion to an ancient seashore 
or a plunge to the bottom of a long -vanished sea. 

You also step into the past when you climb the 
loess bluffs along our large rivers. You return to 
the days when a great glacier invaded Illinois and 
the rivers from the melting ice ran milky with rock 
flour ground up beneath the scouring ice. 

After the rock flour had settled and dried on the 
river floodplains, it was swept aloft by the winds. 
Huge dust storms swirling over the bluff s and near- 
by uplands deposited the rock dust, called loess. 
Snail shells were preserved in the loess but, except 
for an occasional bone or tooth of a mammoth, most 
of the plant and animal remains have disappeared. 

In addition to outdoor adventure, a successful 
hunt provides interesting trophies for your collec- 
tions. Many of science's most valuable fossil finds 
have been brought in by amateur hunters. 



WHAT ARE FOSSILS? 

A fossil is some evidence of a prehistoric ani- 
mal or plant, preserved in rock, that gives a clue 
to the characteristics of the organism. The remains 
of animals or plants that lived during historic time 
are not considered fossils. 

The oldest fossils in Illinois are found in rocks 
such as sandstone, limestone, or shale. Some are 
only impressions of the outside of a shell; some 
are fillings of the inside. 

Parts of the original shell may be preserved, but 
in many fossils the hard parts of the animal have 
been replaced by a material different from that of 
the original. Silica and calcium carbonate, which 
are easily preserved, commonly replace the ori- 
ginal shell material. 

Some fossils were made by marine worms which 
burrowed in the sand or mud of the sea floor. The 
worms themselves are rarely found as fossils but 
their trails and holes are common. The burrows 
and holes are fossils just as much as the animals 
themselves would be if they had been preserved. 

In many places in Illinois, shells of clams, snails, 
and brachiopods are preserved with little change 
and are much as they were the day they were buried 
on the floor of a now-vanished sea. 

The plant-fossil materials that make up the coal 
beds of Illinois are the remains of primitive trees 
and plants that lived in swamps during the Coal Age. 
When the plants died they fell into the water and 
were preserved as peat that later became coal. 

Many fine fossils found in the coal and overlying 
shales represent the roots, trunks, and leaves of 
the plants. A few of the insects that lived in the 
trees also are preserved. 



Among the youngest fossils found in Illinois are 
the teeth and bones of bison, giant beavers, deer, 
and elephant-like animals called mammoths and 
mastodons, which lived during the Ice Age. Com- 
plete skeletons of the animals are rare, but teeth 
and tusks are on exhibit in many museums. 



L-^»W& 



Woolly Mammoth 
(After drawing by Charles R. Knight) 



WHERE TO LOOK FOR FOSSILS 

1. Quarries are excellent places to find fossils 
because so much rock is exposed. Old abandoned 
quarries are best for collecting because the rocks 
have been weathered for several years and the fos- 
sils generally stand out in relief. 

If you plan to collect in a quarry, be sure to get 
permission to enter it. In that way someone will 
know where you are in case of accident. In active 
quarries there is danger from falling rock during 
blasting. If the quarryman doesn't know you are in 
the quarry, he cannot warn you when he is going to 
set off a blast. 



2. Some of the best collecting sites in Illinois 
are in the cliffs and bluffs along our major rivers, 
the Mississippi, Illinois, Ohio, Wabash, and their 
tributaries. At these places whole fossils are often 
weathered out and may be picked up easily. 

3. Well-known collecting sites for plant fossils 
are the coal strip mines of Illinois. Perhaps the 
most famous is the Mazon Creek area near Braid- 
wood in northeastern Illinois which has supplied 
beautifully preserved impressions of ferns, tree 
leaves, and a few insects to museums throughout 
the world. Many strip mines also yield fine brach- 
iopods, snails, clams, and cephalopods. 

4. Highway cuts through bedrock commonly ex- 
pose beds containing fossils. Be careful along road 
cuts, especially if there is heavy traffic. 

5. Ice Age fossils, such as mammoth and mas- 
todon teeth and tusks, have been found mostly in 
gravel pits but also in foundation excavations and 
ditches in all parts of the State. 

6. Most of Illinois' major rivers have banks of 
wind-blown glacial dust called "loess." The shells 
of air-breathing snails which lived during the Ice 
Age are common in the loess. 

7. Actuallyyou canfind fossils almost anywhere, 
in the gravel or crushed stone of your driveway or 
in stone walls and foundations. You may see fossils 
in many places where you can't collect them, such 
as counter tops in restaurants, utility marble in 
public buildings, in stone sidewalks in several of 
our older cities, or in riprap along the shores of 
Lake Michigan and our major rivers. 



TOOLS FOR COLLECTING FOSSILS 

1. Hammer - a bricklayer's hammer will work 
well. 

2. One or two cold chisels, preferably one large 
and one small. 

3. Knapsack or basket in which to carry your 
fossils. 

4. Old newspapers or a roll of tissue paper for 
protecting fragile specimens. 

5. Magnifying glass or hand lens, 3 to 10 power. 

6. Pencils and paper for labeling the specimens. 
Much of the value of a particular fossil lies in know- 
ing where it was found and the bed it came from. It 
is important to keep records of your collecting. 




TIPS ON COLLECTING FOSSILS 

1. When you look for specimens in a quarry or 
on a shale slope, sit down or get on your hands and 
knees and look carefully. Spend some time in one 
spot before you move on to another. Excellent fos- 
sils have be en found in places that others had passed 
over many times. 

2. If you find a good fossil embedded in rock and 
you are not certain that you can get it out without 
breaking or destroying it, don't spoil the fossil. If 
you leave it, the wind and weather may help loosen 
the fossil from the rock by your next visit. 



8 




SOa 




3. If you do decide to chisel a fossil from the 
rock, be patient and take your time. If possible, 
chisel a narrow trough around the fossil, taking 
care always to point the chisel away from the spe- 
cimen. When the trough is as deep as the fossil, or 
deeper, strike the base of the pillar you have made 
and the fossil should pop out. 

4. Where the rock is very fossiliferous, it may 
pay you to take small blocks of rock and break them 
into pieces with your hammer. In the process the 
rock tends to break around the fossils. If there are 
enough fossils in the rock, you probably will get 
some unbroken specimens. 



FORAMINIFERA 




Hyperammina 
40 X 

Involutina 40 X 



Bathysiphon 



Thurammina 40 X 



Schwagerina 6 X 



SPONGES 




Plcdef 




COMMON TYPES OF ILLINOIS FOSSILS 

FORAMINIFERA (for-am-i-nif-er-ah, plate 1). 
Foraminifera are very small one -celled animals, 
commonly called "forams 
They are important to 
geologists, who use 
them to identify oil- 
bearing rocks. 

_,, , ..- , Fusilina A Foraminifer 

They are beautiful- .. ... , ._ 4 . Iin v , 

3 Magnified 10 times (10 X) 

ly shaped little shells, 

but you will be able to see them clearly only with 
a magnifying glass or hand lens. Some are calcium 
carbonate, others are made of tiny sand grains ce- 
mented together with silica. 

Some foraminifera make their shells of parts 
that come from the skeletons of other animals. 
Some kinds are so particular about the kind of 
materials they use that they select only grains of 
a certain color and size. 

Foraminifera live in tremendous numbers in the 
seas today. They lived as far back as the Ordovician 
period, more than 400 million years ago (see the 
Geologic Time Chart, page 2). 

Calcareous foraminifera such as Endothyra (en- 
doh-thy-rah, plate 1) are very abundant in Illinois 
in the Salem limestone, which occurs in the bluffs 
of the Mississippi River near the end of Mc Adams 
highway northwest of Alton and in the bluff s of Mon- 
roe and Randolph counties. The Salem limestone 
also crops out near Anna and Jonesboro in southern 
Illinois. 

Another kind of calcareous foraminifer, Fusilina 
(few-sil-eye-nah), is very common in rocks of 
Pennsylvanian age throughout Illinois. The little 



fossils look like grains of wheat and are so abun- 
dant in some limestones and shales that they can be 
collected by the thousands. 

For a list of localities where foraminifera are 
abundant, see pages 162-167 of Illinois Geological 
Survey Bulletin 67. 

SPONGES (plate 1). Sponges are mainly marine 
animals that live attached to the sea floor. Fossil 
sponges are 
numerous in 
some parts 
of Illinois. 
They are not 
the flexible 
sponges you 
and I know, 
of course. 
Instead they 
have a hard 
skeleton of 
calcium car- 
bonate or 
silica. The 

oldest ones are known from Cambrian rocks and 
are about 550 million years old. 

One fossil sponge, called the "sunflower coral," 
is common in the Ordovician rocks of north -central 
and northwestern Illinois. 

Another, called Hindi a , is found in Silurian rocks 
exposed in quarries in the Chicago region. It looks 
like a small round ball but, when broken, is seen to 
be made of thousands of radiating rods of calcium 
carbonate. 




Modern Sponges 



12 



u 



.:W- -£'.•;■ '\ ft F i?± K 




Modern Corals 



CORALS (plate 2). Corals are small brightly 
colored marine animals that look much like flow- 
ers. The animal 
grows an external 
stony skeleton 
connected with 
radial partitions 
on the inside 
which divide the 
body into cham- 
bers. The animal 
itself is called a 
polyp and the 
skeleton is called 
coral. 

Some corals 
live together in 
colonies made up of 
hundreds of individuals, 

attached to each other by their outer skeletal walls. 
They sometimes form coral reefs hundreds of miles 
long. 

The skeletons of solitary polyps maybe cushion-, 
horn-, or tube -shaped, each with a depression in the 
top in which the animal lived. The solitary corals 
are referred to as horn or cup corals. 

In colonial forms the skeletons may be either 
branching or closely packed and massive. Corals 
live only where the seas are warm and shallow. 
They are very numerous in today's tropical seas. 
The animals have been common throughout geolo- 
gic timesothat it is easy to collectfine specimens. 

Fossil corals are most common in limestone, 
where they sometimes make up a large part of the 
rock, but they also are found in shale and sand- 
stone. 



13 



BRYOZOA 




Lioclema 6X 



Stomatopora 18 X 

CORALS 




Streptelasma 2 /3 x 



Lithostrotionella 1/2 X 

Plate 2 



Lophophyllum I X 



BRYOZOA (bri-o-zoh-ah, plate 2). The tiny col- 
onial animals called bryozoa generally build stony 
skeletons of calcium carbonate. 







Archimedes 
A Mississippian Bryozoan 
The fronds are commonly called Fenestefla. 

They grow in a variety of shapes and patterns, 
mound-shaped, lacy, tree-shaped, or even screw- 
shaped. Each skeleton has numerous tiny holes, 
each of which is the home of a minute animal. They 
live attached to the sea floor, to stones, or to other 
animals. 

Bryozoa are very common as fossils. The oldest 
ones come from Cambrian rocks about 500 million 
years old, and their descendants live today. 

During the Mississippian period bryozoa were 
so common that their broken skeletons formed en- 
tire limestone beds. Fossil bryozoa may be found 
either in shales or limestones and they occur 
throughout Illinois. 



15 



BRACHIOPODS 




Lepidocyclus 2/3 X 



Rhynchotreta IX 

Pkh3 



Paraspirifer 2/3 X 




Herbertella 1/2 X 



Leptaena I X 

Plate 4 



Platystrophia 2/3 x 




Mississippian Brachiopods 



BRACHIOPODS (brack-e-o-pods, plates 3 and 4). 
Brachiopods are marine animals that have two 
shells, an upper one 
and a lower one. The 
right and left halves 
of each shell are mir- 
ror images but the two 
shells are not exact- 
ly alike. The shells 
may be of lime, phos- 
phate, or a horny sub- 
stance, and they range 
in size from less than 
1/4 inch to several 
inches. 

Most brachiopods live attached to the seafloor by 
a fleshy stalk that is an extension of the soft body. 
Some forms lose the stalk when they become adults 
and either attach themselves directly to the sea 
floor or lie loose in the mud or sand. Some have 
spines that serve as anchors. 

Brachiopods are not common in most oceans 
today, but at times in the past they were the most 
abundant shellfish and sometimes formed large 
shell banks much as oysters do today. 

The oldest fossil brachiopods are found in Cam- 
brian rocks which are about 550 million years old. 
However, the animals became abundant in Ordovi- 
cian time and remained so throughout the Paleozo- 
ic era. 

In Illinois, the fossils are especially common and 
well preserved in the Mississippian limestone and 
shales of the Ohio. and Mississippi river bluffs, but 
you can find them easily in almost any part of the 
State. 



18 




Marine Worm Jaw 
(Greatly magnified) 



MARINE WORM JAWS (plate 5). Marine worm 
jaws are easily preserved and are known in nearly 

every geologic system. Most of 
them are composed of chitin (fin- 
gernail material). They are black 
and shiny and have many teeth. 
Sea worms live today and the fos- 
sil record of worm trails goes 
back to the pre -Cambrian period. The oldest worm 
jaws are found inOrdovician rocks. They are com- 
mon in the Silurian rocks of northeastern Illinois. 

GASTROPODS (gas-troh-pods, plate 5). Gastro- 
pods commonly are called snails. The snail carries 
its shell on its back and retreats into it whenever 
danger threatens. As a snail grows larger it expands 
and lengthens the 
shell. Most com- 
monly the shell 
is coiled in a 
spiral, but some 
are shaped like 
a Chinese coolie 
hat. 

There are many 
kinds of gastro- 
pods. Some live 
in the sea, some :j3 * 
live in rivers,'-.-/ ^^ 
and still others -^Msfig^ 
live on land. The Modern Marine Gastropods 

ones that live in water have gills like fish, but those 
thatbreathe air have simple lungs. Gastropods have 
a distinct head, feelers, eyes, and a mouth. Some 
have a rasp-like tongue. The snail uses its tongue 
for boring into other shellfish which it eats. 




19 




WORM JAWS 





Lumbriconereites 10 X 



lldraites 20 X 



Arabellites 20 X 

GASTROPODS 




Oenonites 10 X 




Trochonema IX 



Bellerophon IX 



PlateS 



Snails are common as fossils in the Ordovician 
and Pennsylvanian rocks of Illinois. Snails that 
lived during the Ice Age are abundant in the loess 
in places along the bluffs of the major rivers and 
may be recovered by washing the loess through a 
coarse screen. 

The oldest snails lived during the Cambrian pe- 
riod, more than 550 million years ago. 




Straight Ordovician Cephalopod 

CEPHALOPODS (sef-a-lo-pods, plate 6). Ceph- 
alopods have beenfound as fossils in rocks of many 
ages, and many are alive today. Squids, octopuses, 
cuttlefish, and the pearly nautilus are among the 
cephalopods presently living in the seas. 

Cephalopods are the most advanced of all animals 
without backbones. They have a highly developed 
nervous system with eyes much like human eyes. 

The cephalopod 1 s mouth is surrounded by long 
tentacles commonly armed with suckers. Beneath 
the tentacles is a tube through which the animal 
can force a jet of water and thus move about by 
jet propulsion. 



CEPHALOPODS 




, ,. ., 9/ v Endolobus 2/ 3 x 

Lechntrochoceras *■/■$ X 

Plate 6 



Imitoceras 2/3 X 



Coiled cephalopods live today only in the South 
Pacific but in the geologic past they were scattered 
throughout the world. Modern squids live in shal- 
low coastal waters over much of the globe. 

Most of the ceph- 

i A** 







alopods we find as 
fossils had a calcar 
eous outer shell. 
Some were loosely 
coiled, some tightly 
coiled, and others 
shaped like a 
tapered tube. 

As the shelled ==== 
forms grew, they *—# 
periodically made 
new and larger shell Modern Co,led Cephalopod 
chambers to fit their bodies and sealed off the old 
part of their shells with a wall of pearly calcareous 
material - hence the name, "chambered nautilus." 

During the Ordovician period, about 450 million 
years ago, some straight cephalopods grew to be 
as long as 19 feet, although most were much short- 
er. Straight cephalopods were common in Ordovi- 
cian and Silurian time; coiled ones became fairly 
common only by Later Paleozoic times. We find 
both in the Pennsylvanian rocks of Illinois. 

PELECYPODS (pe-les-i-pods, plate 7). Pelecy- 
pods include oysters, clams, mussels, and cockles. 
They have been found in the oldest marine rocks 
known and still are very numerous in the seas and 
rivers today. Many of our pearl buttons are made 
from Mississippi River clam shells. 



23 



PELECYPODS 




Myalina 2/3 x 



Clionychia 2 /3* 

Plata 7 



Aviculopecten 2/3 * 



Most pelecypods have two shells which are mir- 
ror images of each other, one on the right and one 
on the left. Each shell has a beak that points for- 
ward and represents the spot where the shell be- 
gan to grow. The top edge of each shell commonly 
has several teeth and sockets that fit into those of 
the opposite shell to make a hinge. The outside of 
the shell generally is ornamented by ribs, spines, 
and growth lines. 




:: : ^^ 



Pecten 
A Modern Pelecypod 

Most pelecypods form shell banks in the seas or 
rivers, on sand and mud flats. Many burrow into the 
mud or sand, and even into wood or rock. Some oy- 
sters attach themselves to rocks and others creep 
about the sea floor by means of a hatchet-shaped 
foot thrust between the open valves. A few (scallops) 
move by jet propulsion, opening the two valves slow- 
ly and snapping them shut to force the water out in 
a jet stream. 

Fossil clams are common in some Pennsylvanian 
rock formations in central Illinois and in some Or- 
dovician limestones in northern and western Illinois. 



25 



OSTRACODES 




Dalmanites V2* 



Isoflus l/ 3 X 



Plate! 



TRILOBITES (try-lo-bites, plate 8). Trilobites 
have been extinct for more than 200 million years. 
They often are pre- 
served ingreat de- 
tail and are prized 
as fossils. Two 
grooves extending 
down the back of 
the animal divide 
it into three lobes, 
hence the name 
"trilobite." 

Trilobites had a 




Ordovician Trilobite 



head with eyes and a mouth, a jointed body, and a 
tail. The animals were cousins of the crabs and 
lobsters and lived in the sea. 

They were covered with a horny armor, jointed 
so the animal could move. Trilobites shed their 
armor much as snakes shed their skins, so each 
animal could have provided several fossils. 

Trilobites were abundant in Cambrian, Ordovi- 
cian, and Silurian times and were among the most 
important animals then on earth. They became ex- 
tinct during Permian time. 

OSTRACODES (os-trah-cods, plate 3). Ostra- 
codes are very small animals which are common 
as fossils but are rarely large enough to be seen 
by the naked eye. 

They have been present on earth since the early 
part of the Ordovician period, and occur today in 
great numbers in lakes, rivers, and seas. Ostra- 
codes prefer shallow water and live in vast hordes, 
crawling over the bottom or swimming near the 
surface. 

They have two shells, one on each side of the 
body, so that some ostracodes look much like small 



27 



GRAPTOLITES 




CYSTOIDS 








Tetragraptus I X 



Caryocrmites IX 
Dendrograptus 40 X „ o/ocys „ 7es y^ BLASTOIDS 




Pisocrinus IX 



Crinoid Columnals IX 



Pentremites 2/ 3 X 



AU? <? 




Ordovician Crinoid 



clams. But the animal inside looks much like a 
shrimp or an insect with jointed legs and feelers. 
As the animal grows, it sheds its shells and forms 
a new pair. The shells maybe smooth or ornament- 
ed with pits, bumps, ribs, or spines 

CRINOIDS (cry^noids, 
plate 9). Crinoids 
are called "sea 
lilies," but they 
are animals ra- 
ther than plants. 

They look like 
plants, however, 
because the body 
skeleton or calyx 
generally is on 
the end of a stem 
made of button - 
like discs and held on the sea floor either by a stony 
anchor or root-like arms. The mouth, on top of the 
body, is surrounded by arms which sweep food into 
the mouth. The body is made of calcareous plates 
which fit together like irregular bricks. 

When the animal dies, the plates and discs tend 
to fall apart and sink to the sea floor. Many of the 
limestone beds in Illinois are composed mostly of 
crinoid plates and discs. 

The complete calyx is a highly prized fossil. Good 
ones are found in the limestone cliffs along the Mis- 
sissippi River between Burlington and Alton. 

Stems or stemdiscs are common throughout most 
of Illinois and popularly are called "Indian beads" 
or "fish bones." The oldest crinoids come from Or- 
dovician rocks. Some crinoids live today, mainly 
in deep parts of the ocean, but they are not nearly 
so common as in the past. 



29 



BLASTOIDS (blas-toyds, plate 9). Blastoid fos- 
sils commonly are called "sea buds." They are 
closely related to crinoids but differ from crinoids 
in that instead of arms they had small hair -like 
pinnules which swept food into the mouth. The soft 
pinnules rarely were preserved. 

Some blastoids had stems but others did not and 
were attached directly to the sea floor. Like cri- 
noids, they had a mouth at the top of the body (calyx) 
surrounded by small round holes that conducted 
water into the body. 

The oldest blastoids, found in Ordovician rocks, 
lived about 450 million years ago. The animals sur- 
vived until the Permian period, about 225 million 
years ago, when they became extinct. Blastoids are 
beautiful fossils which look much like small hickory 
nuts. 

They most commonly are found in the river cliffs 
and stream banks of western and southwestern Illi- 
nois, especially in Randolph County, and in southern 
Illinois near the Ohio River. 

CYSTOIDS (sis-toyds, plate 9). Cystoids are re- 
lated to the crinoids and blastoids but are more 
primitive than either. The body, or calyx, is not 
nearly so well developed and the arms are irregu- 
lar and rarely preserved. Nearly all cystoids are 
stemless and the body plates are quite irregular 
in arrangement. 

The cystoids lived from the Ordovician period, 
400 million years ago, until the Mississippian per- 
iod, 300 million years ago. 

Most cystoids found in Illinois come from quar- 
ries in the Silurian rocks in the Chicago region and 
in the Mississippi River bluffs of northwestern Il- 
linois. 



30 




Ordovician Graptolite 



GRAPTOLITES 
(grap -toe -lite s, 
plate 9). The grap- 
tolites were a very 
simple kind of ma- 
rine animal that 
appeared in the 
Cambrian period. 
They became abun- 
dant in Ordovician 
and Silurian time 
but gradually died out, 
The last ones lived during the Mississippian period. 
The animals lived in tiny chitinous cups arranged 
along slender stems. In some forms the stem was 
attached to a round float, and in others two, three, 
or four stems might be attached together. Most 
graptolites floated free in the oceans and were 
scattered throughout the world. 

As fossils, they look like little black lines with 
saw-tooth edges. They are found mainly in shales 
but also occur in limestones. In Illinois they are 
most common in Ordovician rocks of the northern 
part of the State. 

CONODONTS(ko^no-donts, 
plate 10). Conodonts are 
small fossils which bare- 
ly can be seen by the na- 
ked eye. Almost nothing is 
known about the animal 
these beautiful amber-colored tooth-like little fos- 
sils came from. 

Even though we don't know much about them, co- 
nodonts are of value because they help geologists 
determine the age of the rocks in which they are 
found. 




Mississippian 
Conodont (40 x 



31 




Lepidodendron 2/5 X 



Annularia 2/5 x 

VERTEBRATE FOSSILS 



Mammoth tooth i/gX 







tevrts«| 

Stigmaria 2/gX 




Mastodon tooth '/ 6 X 



Plate fO 



Conodonts of the same type are found over much 
of the world in rocks of the same age, leading us to 
believe that the animal was a good swimmer and 
could cover great distances. Because of this, we 
think these fossils may be those of an extinct fish. 

Conodonts have been found in rocks ranging from 
the Cambrian to the Trias sic. They are found in 
bedrock formations throughout Illinois. 

PLANT FOSSILS 
(plate 10). Of all the fos- 
sils that have been found 
in Illinois, perhaps none 
are more famous than the 
fossil leaves and other 
plant remains from the 
world-renowned Mazon 
Creek area in northeast- 
ern Illinois. 

In this area, which lies 
in Grundy and Will coun- 
ties, iron carbonate nod- 
ules containing plant re- 
mains are found in the 
waste piles of strip and 
underground mines and at 
places along Mazon Creek. 

The plant fossils are 
remains of fast-growing 
ferns and trees. In the 
damp lowlands and swamps that covered Illinois dur - 
ing the Coal Age, they formed a dense growth and 
were preserved in our coal beds. 

In the jungle -like growth the plants most common 
were huge ferns that had fronds five or six feet 
long and grew to a height of more than 50 feet. Along 
with them were seed ferns, now extinct, and giant 

33 




Lepidodendron 

A Pennsylvanian 

Scale Tree 



scouring rushes, descendants of which are the small 
horsetail rushes that live today along our wooded 
streams. You can recognize scouring rushes by their 
jointed trunks and the leaf whorls, common in the 
Mazon Creek nodules. 

The most imposing plants of the Coal Age forests 
were the scale trees, which grew to heights of 100 
feet or more. Close-set leaves grew on their trunks 
and limbs, and when the leaves fell off they left rows 
of scars that are the identifying marks for the trees. 
Diagonal rows of scars identify the Lepidodendron 
and vertical rows identify the Sigi/laria. 

VERTEBRATE FOSSILS (plate 10). Animals 
with backbones are called vertebrates. They include 
reptiles, amphibians, fish, birds, and mammals. 

In many western states, vertebrate fossils, such 
as skeletons of dinosaurs, camels, and saber-toothed 
tigers, are common inMesozoic and Cenozoic rocks 
(see Geologic Time Chart, page 2). 

IfMesozoic and Cenozoic rocks were ever depos- 
ited in Illinois, they have been removed by erosion. 
As a result, the vertebrate fossils found in our 
State are restricted to Paleozoic and Pleistocene 
rocks. 

The Paleozoic vertebrate fossils are fish teeth, 
scales, and bony plates, a few lizards, and amphi- 
bians. The Pleistocene vertebrates included many 
forms now extinct, such as mammoth and mastodons, 
and many forms still living in this region, including 
man. 



34 



BOOKS ABOUT FOSSILS 



FIRST BOOK OF PREHISTORIC 
ANIMALS. Alice Dickinson. Frank- 
lin Watts, Inc., New York, 1954. 

A beautiful little book for grade 
school age. Well written and well 
illustrated. 

HOW THE WORLD BEGAN. Edith 
Heal. Thomas S. Rockwell Co., 
Chicago, 1930. 

The story of the beginning of life 
on earth. For advanced grades 
through high school. 

THE STORY OF OUR ANCESTORS. 
May Edel. Little, Brown and Co., 
Boston, 1955. 

Tells how man grew into the 
strange upright creature that he is 
with nimble fingers and giant brain. 
For junior high and high school. 

LIFE LONG AGO. Carroll Lane 
Fenton. The John Day Co., New 
York, 1937. 

One of the very best books for 
advanced grade and junior high. 

STORIES READ FROM THE ROCKS. 
Bertha Morris Parker. Basic Sci- 
ence Education Series. Row, Pet- 
erson and Co., Evanston, 111., 1942. 
Advanced grade and junior high. 

ANIMALS OF YESTERDAY. Bertha 
Morris Parker. Basic Science Ed- 
ucation Series. Row, Peterson and 
Co., Evanston, 111., 1948. 

Advanced grade and junior high. 

COMMON FOSSILS OF MISSOURI. 
A. G. Unklesbay, University of Mis - 
souri Bulletin, Handbook 4, Colum- 
bia, Mo., 1955. 



OHIO FOSSILS. A. LaRocque and 
M. F. Marple. Ohio Division of 
Geological Survey Bulletin 54, 
Columbus, Ohio, 1955. 

A popular account of fossils 
written especially for the amateur. 
It has several keys for identifica- 
tion of fossils. 

LIFE OF THE PAST. G. G. Simp- 
son. Yale University Press, New 
Haven, Conn., 1953. 

A broad and very readable in- 
troduction to the study of fossils. 

PREHISTORIC ANIMALS. William 
E. Scheele. World Publishing Co., 
Cleveland, Ohio, 1954. 

A beautifully illustrated book for 
all ages. 

THE WORLD WE LIVE IN. Time, 
Inc. (distributed by Simon and 
Schuster, Inc., New York), 1955. 

A superb general survey of the 
world of nature. Two chapters are 
devoted to life of the past. 

DINOSAUR BOOK. E. H. Colbert, 
American Museum of Natural His- 
tory, New York, 1945. 

Excellent popular summary of 
our knowledge of dinosaurs. For 
all age levels . 

HANDBOOK OF PALEONTOLOGY 
FOR BEGINNERS AND AMATEURS 
Winifred Goldring. New York State 
Museum, Albany, N. Y., 1929. 

A summary of paleontology for 
adults. 

FIELDBOOK OF ILLINOIS LAND 
SNAILS. Frank Collins Baker. II- 



linois Natural History Survey Man- 
ual 2, Urbana, 111., 1934. 

A beautifully illustrated booklet 
that will aid in identifying most 
Pleistocene snails. 

INTRODUCTION TO HISTORICAL 
GEOLOGY. R.C. Moore, McGraw- 
Hill Book Co., New York, 1949. 

A general account of earth his- 
tory and organic evolution. Adult 
level. 

AN INTRODUCTION TOPALEON- 
TOLOGY. A. Morley Davis. Thomas 
Murby and Co., London, 1947. 

A somewhat simplified outline 
of the major fossil groups. 

MAN AND THE VERTEBRATES. 
A. S. Roemer, University of Chi- 
cago Press, Chicago, 1941. 

A well illustrated introduction 
to living and fossil vertebrates. 



ANCIENT PLANTS AND THE 
WORLD THEY LIVE IN. H. N.An- 
drews. Comstock Publishing Co., 
Ithaca, N. Y., 1947. 
College level. 

PRINCIPLES OF INVERTEBRATE 
PALEONTOLOGY. R. R. Shrock 
and W. H. Twenhofel. McGraw-Hill 
Book Co., New York, 1953. 

Technical college-level textbook. 

INVERTEBRATE FOSSILS. R. C. 
Moore, Cecil Lalicker, and A. 
Fischer. McGraw-Hill Book Co., 
New York, 1953. 

College text. Well illustrated. 

INDEX FOSSILS OF NORTH AM- 
ERICA. H. H. Shimer and R. R. 
Shrock. John Wiley and Sons, New 
York, 1945. 

Useful for the identification of 
most invertebrate fossils. 




EDUCATIONAL EXTENSION PROGRAM 

The Educational Extension Division of the Illinois 
State Geological Survey contacts the public through 
a number of channels, including nontechnical pub- 
lications, rock and mineral collections for Illinois 
schools and educational groups, lectures, exhibits , 
correspondence involving identification of rocks 
and minerals, news items for the press, and field 
trips. 

During each year six field trips aregiven, in wide- 
ly separated parts of the State, for teachers, stu- 
dents, and laymen. The general program is espe- 
cially designed to assist in teaching the earth sci- 
ences and help make Illinois citizens aware of the 
State's great mineral wealth. 

Illinois State Geological Survey 
Urbana, Illinois 



nnmzzi 





£di4axtkmal £>&tie& 4 25 cetdd,